1. Field of the Invention
The present invention relates to bio-nanotechnology, and particularly, to a method of nano-silvering or coating of glass substrates.
2. Description of the Related Art
Nanotechnology coating is a fast growing field that focuses on depositing uniform nanolayers of metals or metal oxides and on dispersing nano-suspensions homogeneously onto a substrate such as glass, metal, wood, automotives, floor, etc. Some nanolayer deposition applications include solar glass, float glass, and eyeglass or lenses. Dispersion applications include, for example, spraying catalyst inks in fuel.
It has been shown that β-diketone curcumin and curcuminoids (1,7-diaryl-1,6-heptadiene-3,5 diones), which are a group of naturally occurring 1,3-diketones constituting the yellow colored physiologically active component of the traditional Indian medicinal plant (Curcuma Longa L.) have potent antioxidant properties and good ligating ability for metal ions. Previously, Curcuma Longa tuber powder was used in the synthesis of silver nanoparticles by stirring a mixture of AgNO3 and C. Longa powder aqueous extract for 24 hours at 25° C. However, the pH factor upon which the chemistry of curcumin is dependent was not addressed.
Silver metal nanoparticles possess the highest electrical conductivity, thermal conductivity and reflectivity of all metals, and therefore, can be used in a variety of applications, such as, catalysis, electronics, photonics, photography and as antibacterial active agents. The reduction process can be either chemical reduction, e.g., using hydrazine, hydrogen reducing atmosphere, or sodium borohydride (NaBH4), or thermal reduction. Silver metal nanoparticles can also be prepared by ionizing γ60Co radiation, ultra violet high radiation and beam radiolysis.
Silver coating of substrates, e.g., glass substrates, are well known in the art. The Tollen's reaction is one example, and involves aldehyde as a reducing agent. Rochell salt, sodium tartarate, or tartaric acid are also used for the industrial manufacture of mirrors. Further, silver coating methods are also disclosed in U.S. Pat. Nos. 5,186,984, and 3,978,271, which are incorporated herein by reference in their entirety.
However, many of the known methods of coating substrates involve the use of hazardous chemicals, consume heat energy, are time-consuming, are economically unfeasible and/or difficult to carry out at a small or large scale. Typically, prior methods use either a spraying technique or vacuum at lower temperatures or temperatures of at least 260° C., while keeping the substrate in contact with the coating solution for hours. Therefore, it would be desirable to provide a benign, simple, quick and economically feasible process for nano-silvering of glass substrates of different shapes and curvatures that overcomes the drawbacks of the prior art.
Thus, a method of nano-silvering glass substrates utilizing a green process thereby, solving the aforementioned problems, is desired.